In semiconductor manufacturing technology, photo processing may be used to accomplish relatively high integration of semiconductor devices. During photo processing, a photoresist pattern may be formed on a substrate using light. Photo processing may be performed in different ways using a photoresist film. The method of photo processing may depend on the types of substrates, the degree of adhesiveness between a substrate and a photoresist film, and/or the reflectivity of an exposure wavelength on a substrate. Photoresist film may comprise an organic compound. If a substrate includes a metal film, unpredictable horizontal and vertical defects may be caused in sidewalls of a photoresist film due to diffused reflection and high reflection from the metal film when the photoresist film is developed. To reduce this effect, a photoresist film may be formed along with an anti-reflective coating.
A metal line may be formed using a metal film. A metal film may include at least one of Aluminum (Al), Titanium Nitride (TiN), and Titanium (Ti). A metal film may be formed on a substrate through a thin film process. A photoresist for anti-reflection may be coated through a photo process along with an anti-reflective coating. An anti-reflective coating may be used to minimize light reflected from interfacial surfaces having different reflective indexes. An anti-reflective coating may include a polymer layer having a desired reflective index and/or a high absorption coefficient for an exposure wavelength that may process a photoresist and the anti-reflective coating.
FIG. 1 illustrates a photoresist pattern 40a over metal film 20. In part (a) of FIG. 1, there is no anti-reflective coating between photoresist pattern 40a and metal film 20. In part (b) of FIG. 1, anti-reflective coating 30 is between photoresist pattern 40a and metal film 20. Photoresist pattern 40a may be formed after forming anti-reflective coating 30. As illustrated in the lower part of FIG. 1, photoresist pattern 40a may be formed with less distortion when anti-reflective coating 30 is used (e.g. see comparison of part (a) and part (b)).
Photoresist pattern 40a may be formed by coating photoresist material over metal film 20. Photoresist material may be coated over the entire surface of metal film 20 by rotating a substrate at a high speed. A solvent of a photoresist material may be vaporized and removed through a baking process at a predetermined temperature, thereby hardening the photoresist material. An exposure process may be performed using mask 50 as a stepper. In this exposure process, rays of ultraviolet light 60 may be projected onto the photoresist material through photo mask 50 to form photoresist pattern 40a from the photoresist material. From the attributes of mask 50, a micro circuit pattern may be formed associated with the pattern of photoresist pattern 40a. A micro circuit pattern may be a metal line pattern of a semiconductor device. Metal film 20 may be etched using photoresist pattern 40a as a mask. A process of etching metal film 20 may include separate steps of etching anti-reflective coating 30 and etching metal film 20 to form metal lines.
As illustrated in FIG. 2, polymer-based particles 30b may be incidentally deposited on the anti-reflective coating 30, when anti-reflective coating 30 is etched. Polymer-based particles 30b may drop to metal film 20 during processing, as illustrated in FIG. 3. Existence of polymer-based particles 30b may reduce a yield rate of semiconductor device manufacturing.
As illustrated in FIG. 4, if a metal line is formed using only photoresist pattern 40a (without forming an anti-reflective coating), footings 40b may result on photoresist pattern 40a. Footings 40b may be caused by NH3 or NH4+ existing on the surface of metal film 20. Along with reflection complications caused by the absence of an anti-reflective coating, footings 40b may prevent a metal line pattern from being etched.